Semi-automatic telephone system.



C. .l. ERICKSON. SEMI-AUTOMATIC TELEPHONE SYS'YM.

AFPLICAHON FILED APR. H, 1913,

Patented Apr. 1917..

z T r H mm cafe/ Patented Apr. 3, 5 SHSETS -SHEET 3.

C- ERICKSON.

SEMI'AUTQMA'HC TELEPHONE SYETEM. APiLICATION FILED APn. I1, 1913.

fM/ENTO/P:

TQEIVEYS.

mywisaza '01. ERICKSON,

SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLECM'EUN FILED APR. IT- 1913,

- Patented Apr. 3, 1917.

R f a we" H M ,y N W 5 L H m Mm A J m K fi M 7 n LTT &@ 2 W w El A 7 m 4 37% m m 3 ME NW n9 3 1w 1 i Q APPLICATION HLED APR. 1?, I913- PatentedApr. 3, 1917.

M Q @Q@ particula rly Martin, Serial No.

STATES IPATEENT OFFICE,

cmmms J. mucxson, or cmcaoo, rumors, assmnon T0 nu'roma'rrc iamic'rmc' comment, or cmcaoo, rumors; concurrence rumors.

sEuI-Amonurc TnLErfion-E srsrma.

To all whom itvmag concern:

nois, have invented a certain new and useful Improvement in- Semi-Automatic Tele-.

phone Systems, of which the following is a specification. y

. My invention relatesto improvements in semi-autol'natic telephone systems, and more to means for indicating to an operator in such a system that the called line is busy, and is in the nature of an improve ment upon the applications ,of Talbot G. 754,801 filed March 17, 1913, and Michael Schwartz, Serial No. 7(39,284, fi1ed May 22, 1913.

' More particularly, my invention relates to the provision of a supervisory signal on the operators board, and means for flashing this signal when an automatic swltch at tempts to make connection with a busy line.

lleretofore various means have been devised for giving such a signah'but in these systems'it has either been necessary to employ a special form of connector switch, or

else )rovide other s iecial feat!u'esassociated with the busy signaling machine. By my invention I employthe' regular busy signaling current for controlling the operation of this signal, and do away with the necessity of providing any special features in connection with the 'onnector switch. V

A further liiiject of my invention is the provision of a special form of relay'which is bridged. across the trunk line and is responsive to the alternating busy signaling current, which relay controls the o eration of the supervisory signal, the flas ling of which constitutes the busy signal for the operator.

These and other objects of" my invention will be more readily understo'bd by referen'cev to 'the accompany ing'drawings, in which Iha've illustrated my invention 'in conned tion with a semi-automatic'telephone system of one particular type. It will, of course,"

be understood that other forms of cord cir cuits and automatic switches can be employed, and that the dlsclosure is merely for I the purpose of setting forth one particular embodimentpf my invention.

Specification Letters Patent. Application am April 17, 101:. mm 80. 701,501.

In the drawings Figure 1 is a (liagrammatic lay-out of a telephone system" in which I have chosen. to illustrate my invention.

FlgS. 2, 3 and 4 show a complete connec tlon between a manual line and an automatic line in" said system. T

Figs-5, f3 and 7 arev top, side and end v ews,"respectively, of a vlbratory current relay for accomplishing certain objects of the invention, as will be fully described hereinafter.

The telephone system illustrated automatic exchange A. In the manual exchange M thereis re presented a switchboard. comprising a plura1i;y of A or subscribers operators positions ing operators position M; At S? and. S

there areshown twongroups of subscribers substations S, each of which is provided at the central, office wish an answering jack J on one A operators position and a multiple jack J on each A-o perator s posltion in the usual manner. Suitable plug cords C are provided for connecting the lines for conten. The subscribe] s substations T and the a a lines connected the reto are divided into groups T, T, T, etc., usually of one hunred lines each. On a scale ofthree. to ten,

therefore, the three groups T, T and T 'represent one complete thousand and the groups T, T and T represent another thousand. With each group of subscribers" lines there is associated in the central ofiice '1 a group of individu 1-1 or line switches D, one for each h connectors switches rep el'itec herein comprise banksof contacts arra gem-1 horizontal rows or levels, usually ten in number. These groups are represented diagrammatically by horizontal lines.- which extend across a group iof switches, thereby indicating that the corre- Pauented Apr. 3,1917. L

v in Fig. 1 1 comprises a manual exchangeM and an M and a B or trunki a gro up of first selectors, E, a group ofsecon selectors F and a group of;

"lhoselector and connector sponding contacts of all the switches of the group are multipled together. All the line switches D belonging to a single group of subscribers lines have common, access. to a group, of firstselectors E. The bank con tacts of all the first selectors of corresponding hundreds are multipled throughout: the diflererit thousands, The'fir st level of bank contacts of these; first-selectors are connected to trunk lines leading,,to second selectors associated with the first thousand,

the contacts of the second level are connected, "I

to trunk lines leading to second selectors F associated with the second thousand, etc.'

All the second selectors associated with a giventho'usand are multipled together, and the first level is connected to trunk lines 'leadin'gto' connectors which have access to Y the lines of the first hundred group of that thousand. .The' second level of the second selectors is connected to trunk lines leading toconnectors havingacce'ss to the lines of thesecond hundred of the thousand, etc.

This trunking arrangement of an automatic art, and it is not thought necessary j scribe it' in greater detail hereini exchangegis in {general well known invthc to dc-s tioned, leads from multiple jacks J 2 on the A-operators positionto a selector switch E in the automatic exchange and is provided at;the,B,-o erators position with the equip:

i; mentI. fl is trunking equipment comprises a calling lamp 14, a disconnect lamp 15, listeningand calling device keys K and, K

and. suitable relays for controlling thevari 'ous circuits The relay 16 is an ordinyy polarized relay-=that is, a relay which attracts its armature in one direction when it receives current of one polarity, and, which attractsits armature in the other direction when it receives current of the opposite polarity. This trunk is also provided with a relay 202 whichis shown in detail in Figs. 5, 6 and 7 and which is represented diagrammatically in Fig. 2 by the coils 202 and 203, armature 212' and spring 215. relay is adapted to be bridged across the line through the condensers 226'and "227 This and the' res'istance 228 by: the' relay 229.

The connection between the. relay 202 and the resistance 228 is grounded. ':The .key K is for the-purpose of connectingthe ordinary In order toforni'means-of communication r between the manual ,and' automatic ex- 8 0 hanges, there are provided a. mumber ol" trunk lines leading from multiple jacks J? 9 on' the manual switcli board "to selectorswitches E at the aiito inatiexchange. .The

bank contacts {of these selectors may be con-' nected in multiple withfl those ofsomeof operators listening and talking set with the,

trunk,-while the key K-' is for'the purpose: of connecting the calling device with. the

trunk, through the med um of, which .the

operator may control the automatic switches the subscribers first"selectors. These trunk,

- selector switches disclosed in United States 1 lines. leading from the jnanual switchboard .to the automatic exchange pass through a trunking or B-eperawrs' position M where they are 'proi rided fwith certain; equipment to usual receiver;2, transmitter 3, induction coil '4, ringer .5 and condenser 6.' At the central oflice the line of the substation S is pro;

.vided with the usual answerin ,jack J aplurality of multiple'jacks J", line relay 7, line lamp 8- and cut-off relay 9, 'The cord circuit C is a well-knowntype ofcord ci'ricuit, com the :usual answeringand calling p ugs P and P" inductively at-- lays 10 and 11 areincludedin' one side of I visory lamps 12 and 13; Thetrunk circuit leading from the manual "exchange to'the in, connection therewith. v The manual teleghone S, (Fig, 2) is anordinary commonattery manual telephone, comprising the 9 to set up the proper connect on, This call 'ing device may be ofiany 'desireditype, such,- forinstance, as that shown inBritish patent to Sr-GrS. DickenNo. 29,654of1910.

Theaautomatic selector switch E as rep: resented herein, is .of the generali,-type, of

Letters Patent No. 815,321, granted March a 13, 1906, to Keith, Erickson and Erickson,

1 comprising supervisory/relays a gn so as to. adapt the switch-to, operate in asy the circuits being modified, however, in a manner similartoithat shown inLBritish Q P t 170 S. G. S, DlCker T No 129 0i I temin which the central oflice ,apparatus isj controlled by impulses delivered overQthe two sides of the line in series. Among other 9 1 details, the seleetor comprises a 'bank ofcontacts arranged m, horizontal rows or levels and which. are adapted to be enga edby set oi wipers 18 ,19 and20 carrie upo' a shaft hav ng a vertical ,movement controlled bythe vertical magnet 21 and a'rotary movement. controlled by {the rotary magnet 22 f The usualside switch comprising the wipers 23, 24, 2 5 and 2 6 is controlled by the. soe

gknown in the art. The operation of the repeating'coil R. 'The usula-l supervisorv re- 1 is automatic exchange, as has been'before menv v "fswitch is controlledthrough the mediumofnected together throu'gh the medium of a 29, 30 and"'31 are'slow"actingrelays that I Y is, relays which deenergize slowly. Means the cord ClIC-Jlt for controlling the superfor releasing the switch are provided in the release magnet 32) whichlmagnet releases the swltch immediately "upon energizing,

rather than by its deenergization as shown called private magnet 27 in a manner well" the of the general type of disclosed in United States Letters Patent No. 815,170, granted March 13, 1906, to Keith, Erickson and Erickson, the circuits, however, being modified so as to ada t it tor operation in a systern in which tie apparatus is controlled over the two sides of the line in series. The mechanical features of the cormector are somewhat snnilar to those ot the selector switches. It comprises a set of wipers 35,

36 and 37 carried upon a vertically and r0- tata'bly n'iovallle shaft, which shaft is controlled by the vertical and rotary magnets 38 and 39 and a side switch comprising the wipers 4.0, 41, 42 and 43' which controlled by the usual private magnet -l-4l. The line relay 45 is connected. with the line through springs controllm'l by the leach-bridge relay 46, tl'irough the w' idings of whichrelay the called tele )honc is Sllpl'llldd with talking current. he relay 47 is a ringing relay, through the-medium of which the application of ringing; current to the called line is controlled. 48 s the usual release magnet. The; two pair." 1." springs 49 and 50 are held. open. by tl switch shaft as long as it is in its normal polsiti'on.

The slilbscrl liriiflual switcl'i l) is of )e of siilbscribcrs switches dis-- closed in British patent to R. W. James No. 26,301. of 1000, being of the particadar form, however, shown in British Patent No. 1298 the general of 1910 hereinabo're referred to. A group of these subscrd'lers' individual switches 1s ordinarily controlled by a so-oalled master switcl'i, but it not thought necessary to descriliiie same herein. The automatic substation T similar to that shown in the said British Patent No. 1298 of 1910.

At Q there shown a busy sigl'ialing machine comprising an induction coil 51, a high speed intmrupter 52 and a low speed interrupter The primary winding of the induction coil 51. is included in a local circuit with the two interrupters'and the battery, whereby an. intermittent interruptcurrent is caused to flow inthe primary windingof said imilnction coil to induce an intern'littent alternating mnirent of high fre- (.uency in the secondary winding. When cormected with t lib 'se'ondary winding into" ,iljiscribers lines, 1; ternating cm'rent .llo produces an interru "i the subscribers There shmvn in. tin of batteries B hayim aaGfor the Imrpose o:

one battery in each exchange.

for operating the central oliice apparatus and for furnishing; talking current. Although a plurality of batteries is shown, one battery only need be used, or preferably lzlelerring to Figs. 5, 0 and 7, it will be seen that the relay .202 in the trunk apparatus I consists of a permanent horse-slum magnet 201 secured to a suitable base 200, which is C(lXIIIPUSQd preferably of non-magnetic inateria. The cores of two small flat electromagnet (oils 202 and 203 are secured tothe poles of the "uagnet 201. Secured to the base 200 by means of'posts 204, 1205 and 200 there a plate 2.0? composed also of non-magnetic material. A thin plate of iron 212, which projects Forward over the ends of the poles of the elertromagnets 203 and 202, is secured to the end of the plate 207 by means of the washer 208 and. screws 209 and 35 210. This plate lllforms an armature or diaphragm for the permanently magnetized electroi'uaguet composed of the permanent magnet 201 and ('ois .202 and 20,3. Secured to the fare of the plate 207 and insulated tl'ierefrrm is a Ion; thin spring 215, which spring extelulsmarallel with the armature or diaphragm 21: and carries at its end a snnall aveight 212-3 and cont let point ll-l. "By means of tln adjustable screw 216, the pressure of the contact point 21+ on thearimiture 212 may be varied. 'lle )ring 215 and armature 212 form termna of the local circuit that is to be controlled by the relay, which circuit normally losed by the engagement of the contact'QH with the armature 212. If an alternating current be transmitted through the coils 2(2 and the armature 212 will be caused to vibrateiin unison with said current in a .naim'er very similar to that of an ordinary telephone receiver diaphragm. This vibrition will be transferred tl'irough t e (JOIIUICI', 21 4 to the weight 213 on the of the spring'fllfir The natural period ofyibration of the spring 215 is very much lower than the frequency of the alternating current whica operates the relay, and tll *refore when the armature 212 vibrated, th' contact 214 dots not vibrate in unison therewith, but vibrites independently in a mg the local. circuit which is controlledby' the relay. This construction produces an a I l ternatmg current relay, WlllCll is very sensitive in its operatior -that is, it may be up eratpd by an alternating current of very hi h frequency ant of very small volume.

In order to term a means of ad jnstmcnt of" the air gap between the armature Zlil and the poles of the magnet, two saw cuts 217 and 218 are made mthe plate 207 alongside and pmgPf the portion to which thearmature 212 is attached, whereby said armature is attached to a somewhat narrow and flexible strip. Passing up through the base 200 there is a screw 215) which engages the under side of the member to which the armature is attached, and by turning this screw the armature may be forced up slightly or lowered to adjust the air gap to the desired width. Electrical connections to the relay are made through the medium of the terminals 220, 221,222 and 223 mounted in a block of insulation 224. Two. of these terminals are connected to the terminals of the coils, one terminal is connected to the terminal 225, which is in electrical connection with the sprin 215, and the other terminal is connected with the armature 212 through the frame of the apparatus.

Having given a generalldescription of the apparatus, I will now describe the operations performed in the process of establishing a connection from the manual substation S (Fig. 2) to the-automatic substation T (Fig. 4). Since the automatic apparatus represented hereinis in general well known in the art, and is fully described in the publications hereinabove referred to, its operation will be described in a more or less general manner. Upon the removal of the receiver at the calling telephone S, the circuit of the line relay 7 is closed in theusual manner, which relay, upon energizing, closes the circuit of the line lamp 8 to signal the operator. The'operator answers the call by inserting the plug P into the jack J, whereby the connection is completed between the line and the cord C. By the engagement of the third conductor of the plug P with the jack J,the circuit of the cut-ofl' relay 9 is closed in series with the lamp The relay 9, u on energizlng, disconnects the line relay 7 rom the line. When connection is extended to the cord, the calling substation is provided with talking current from the battery B through two windings of the induction coil R and through the relay 10. The relay 10, upon energizing, closes a shunt around the lamp 12 through the resistanc 157, thereby shunting sufficient current away from said lamp to prevent it from being brought to a glow. The operator then connects her talking set with the line through the medium of the key K and, upon learnin from the calling subscriber that a subscri er of the automatic exchange is wanted, she inserts the plug P into a multiple jack J ,of an idle trunkrline leading'to the automatic exchange. 'Upon the insertion of theplug into the jack, a circuit is closed from ground at the 'cord over the tip strand to the plug/P and jack J through the relay 158, contact 230, thence through the rigg conductorsof the jack- J an relay 11 to the non-grounded 12 of the cord.

terminal of the, battery B. The relay 158, upon energizing, :closes the circuit of the lamp 14 from ground G through the contact 60, armature 61, contact point 62 and lamp 14 to the battery B. 'The closure of the contact 231 of the relay 158 completes a circuit extending from ground G through said contact 231,;springs 232 of the relay 16, armature 212'and sprin 215 .of the alternating current rela and t rough the relay, 233- to battery B. he relay 233, upon energizing, closes the circuit of the relay 234, which, by opening the contact 230, removes a short-circuit from therelay 72, whereby said relay is includedin the circuit of the relay 158. This relay 72 has a sufliciently high resistance to prevent suflicient current from flowing through 'the relay 11 in the cord to operatively energize said relay, Upon the closure of the contact 231 of the relay 158, a second circuit is closed extendiiig'from' ground G through the sprihgs 231 and 232 andrelay 229 to battery B. The

relay 229, upon energizing, completes the connectionbctween the relay coils 202 and 203 and the line.

Uponnoting the signal of the lamp 14, the .operator operates thekey K to connect her talking set with the trunk and inquires the number of the line desired. Upon the closure of the springs 63 and 64 by the oper- -ation of the key K, a circuit is closed from ground Gr through the relay 65 to the battery. The relay 65, upon energizing, breaks the circuit of the lamp 14 and forms a lock G through the contact 60, armature 61, contact 66 and through said relay 65 to battery.

The relay 65, upon energizing, also operates wiper 24, trun conductor 68, springs 74 and- 73 of the key K, contact 71, relay 16, springs and 69, conductor 67, side switch wiper y ing circuit for itself extending from ground 23 (Fig. 3) and the upper winding of the relay 28 to the battery lead 75, thence through battery B to ground G. The polarized relay 16 is operatively energized in the direction to close the contact 77, thereby completing the circuit of the lamp 15, which circuit extends from ground G through the contact 60, armature 61, contact 66, contact 77 and the lamp 15 to battery. The relay 28 of. the selector E upon energizing, closes 'the circuit of the s ow-acting relay 29.

Upon learning the number desired, the B- operator restores the key- K and operates the key K, whereby the relay 16 is disconnected from the trunkleading to the selector and the calling device" springs 17 are bridged across it Im-itea dQ The operator now opcrates her calling device in accordancewith springs 78, it begins too'perate wipers ste by'step over the ontacts of the 35.

. fw-hich is nowin-second position, w

; the first digit 2, the impulse spri operates to raise the shaft wipers 1 the digits of the number of the desired station, which will be assumed to be 2220. Upon" the operation of the calling vice for separated twice momentarily, breaking th circuit of the sole or line re lay 28. Since the relay 29 is ow acting it does not deenergize during tl e momentary interruptions of its circuit by the. deenergizatioIi'ss-of the line relay 28. Therefore, each time 'said'relay deiinergizes, an impul of cut-r t is transmitted through the ve ical mu'giltg-iii and the slow acting relay 30 The magnet'21 thus receives two impul s and 19 and 20 two steps to a position opposite t is second level of. bank contacts. The 'slow acting relay 30 is operated by these impulses to close the circuit of the private magnet, 27 and maintain it closed continuouslyI fntil after the last impulse is delivered.

last impulse is deli red-to the vertical mag net, e side swi is tripped from first second position a'n a wellknownman The movement of the side switch wip 25 from first to'second position disconnec/the battery from the vertical magnet and closes a circuit through/the rotary 'agnet 29. in series withythe relay 31. 'nce the rotary magnet' is, provided with erriipter a manner similar tothat of a buzzer t advance the level tow ich they have been raised by the previous operations of the vert cal magnet.

his operation of the rotary magnet continues as long as the side switch remains-in second position. 2 If the first trunk line of the level is idle, however, the side switch will be trip ed hom second to third positionjnpon .the rst etc of the wipers. If this trunkis busy, howe er, the private wiper 1 8 lis the contact w ch it engages provided ith a guarding ground potential and com'pl an ergizing circuit through th i wr not 27 by way .offthe side switch hypgr 2116, re. y t e saidgmagnet is energized and locksthe said to third osition thecircuit of the rotary side switch in second position. The rotary magnetth'erefo-re continues to rotate the wipers until an idle trunk line is found, whereupon, sincethe private wi er 18 no longerfindsa grounded contact, t e private magnet 27 dener 'zes and the sideswitch' passes from secon to third-position. Upon the movement of the side switch from second magnet 22 is broken, the line relay 28 is disconnected from the line and the line connec tion' is-extended through the wipers 19,-and

2.0 and the contacts and-81 to the second selector F, whereu on its line relay 83 becomes 'energrized an closes the circuit of the pen the deenergization of tljzgrivate magnet after the he relay 8*. upon energizing,

rotary magnet, and being a slow a ctingrelay remains energized for. an instant after the rotary magnet has operated for the last time and the side'owitch has passed to third position, whereb a guarding potential is immediately supp ie'l to the selector private bank contacts of the selected trunk from ind G through the springs 88 and 86 I the side switch wiper 26. An instant bntacts from ground G of the selector F iiver the circuit above traced, and the relay 31 deenergizesin time to close the circuit for the relay 29 before it has time to de'einergize.

- Upon the operation of the operators callingedevice for the second digit), the selector F' operates in the same manner as explained for the selector E .to extend the connection over the trunk; conductors 89, 90 and 91 to the connector H. (Fig. 4 whereupon the connector line reay 45 becomes energized and closes the circuit of the relay 92, which operates to provide a holding circuit for the relays 84 and 29 of the selectors F and E. This circuit'extentls from ground G through thesprings 93, conductor 91, wiper 95, side switch .wiper 96 (in third position), springs 197 and 198, then me through the relay 84 to battery and also in multiple therewith through the side switch wiper 34 (in third position) to and through the relay 29'of the selector E, over the circuit hereinbefore traced to. the battery lead 7 5.

The operator uow operates her callihg device for the third di it 2-,fthereb causing the I conn "tor line re ay. 45 to er a second potential is supplied to said eener ize twioemoi erttarily. The relay 92 being s ow acting remains energized during the .momcntary-interruptions of its circuit, so-that each'time the rela '45 deenergizes, an imulse is tm'nsmitle 0v r the circuit extending from ground G through the springs- 97 and 98, Spring 99 and its front contact, relay 100, vertical magnet 38- 'and the side switch wiper 42 to the battery lead .7 5. The" vertical magnet 38 receives two impulses 'over this circuit and operates to raise the shaft wlpers 35, 36 and 37 two steps The relay 100.is energized by thcseim ulses and operates to close a circuit exten ing from ground Gr through the springs 101 and 102 and prrivate magnet 44 to the battery lead '75. he relay 100 being slow actingdoes not allow its armature to fall back untyiiia [afterthe last impulseis delivered'ztothe ver tical magnet, whenitbreaksthe circuit of the private magnet 44, which in turn deenergizes: and permitsithe sidefiswitch .to pass; t ov second position. The side-switch wiper 42', in passing fromfirst to-second positlon, transfers .the battery connection from the vertical magnet 38 to the rotary ma et 39. The operator now operatesher cul in'g .device -for the last digit; 1),, whereby. the en, ergizing circuit of} the v connector line; relay 4:5 is broken tentimes. 1- Each time; the 1 re:- lay 45 ldeenergi zes in;t his instance, tun-Min pulse is transmittedoventhe circuit-extends ing fronrground :Gf throughthe springs 97 and 98 ,spring Q91 ,and itsfront' contact, relay V100, springs 103 rot ary, 1nagnt 3%), and the side switch wiperi'tz (in; second positionlr-to thelbettery lead 75.:,'l 1,1e rotary magnet op?- ;erute s .in resfp,onse to tllflserignpulses tostep thewipers ifi, 36 'andBY tensteps onto-the contacts of the, desi ged, line; while-the relay 100 operates-inthe same nriuuer. as .for the previous digit to, cause ,thevprivate magnet {14 to advance .thmside switch 'one Stepthat is, fromsecond to. third POSll() l1,- -i1ftel' the lastimpulse for the digit is delivered.

and to. third position finally completes the. tullting connection with themalledgtele; phoiie. ..,-The wiper 4:0,;i1ponmeuchiug third position establishes, a= guarding groundi 1X):

tential at theconnec tpr,private illanlr-con tactsl o'f 'the called line,- and; also provides mi energ zing c rcuit fo-r tl e, cut-oft indlng 104.- of th sul scr befls, indu'lluiil switch D. Th is .circuit enter ids trour ground G" through the .sid'e switch .wipexj; 40,;@shuft wiper 35, private bank contact 105 arid-also to the; corresponding contarts pf; all; theotheij connectors which: 2 ve accesstc the line T and through. the ex -off windmf .10A

ofthelswitch D to tlie batteiiy-lead {the winding ,1.Q4 upon; energizing, attfructs the and 10' p ngto trunkin r ng mp sted he din, the

operator restores theltey K (Fig. 2) to'its normal position, whereby the calling device is disconnected from the trunk and the circuit of the relay 16is reestablished. The relay 16 again energizes to close the circuit of the lamp 15," said rela of, course, having been denergized whi e therall was being set up. When the subscriber at the called telephone T removes his receiver, or as soon thereafter as the ringing-relay 47 deiinergizes, if it happens to-be energized at the time, said telephone is provided with talking current over a circult extending from ground G9 at the .con-

hector Hithrough the leftfhand winding of the back-bridge relay 46, private magnet springs ,2112, thence over the heavy conductors through. the shaft wiper 37 thence to and through the substation-T and backover the other side of the line, through the springs 108 and 107, wiper 36, private magnet springs 113 and theri-ght-hand-Winding of the relay 46 ,to'thc, battery lead 75. The relay 46., upon energizing, transposes the connections-between the windings of the linerelay 515 and'the trunkrconductors' 89 and 90, whereby. thedirection of current flowing through the relay i16'-(Fig. 2) is reversed. This reversal ofthe current causes the relay 1 6 to open the contactu'fi' to extinguish the lamp L5 and \toopen theeeontact232; whereby-the circuitsof the-L'relay 233 is broken,'

which in turnbreaks. the circuit of the slow acting relayzfli l, therehyJ short-circuiting the high resistance relay '72. The short-circuiting QZE.rtl1iS- relay reduces theresistance in the circuit of-the relay.- 11- of" the :cord 0 sufiiciently to .cause' said relay to energize to shunt th'eilam'p 13 by the resistance 117, thereby ca'nsingit to beextinguished. Thus, through the medium :of, the. lamps 1 5 "and 13,.v-both thef BiandA operators are notified vwhen the called subscriber answers;

A further-i result of the energization of the relay 46-of the connector Ill-POIITthQ response 015 the called subscriber. is '-'the' closing-Jot a circuitthrough the "relay 118 which circuit extends iromi ground 2G through the. side switcllnwiper i0, springs .119- -and 120 and the :relay; 118 ;tolnthesbatterylead- 7 The relay 118, iponeenergizing; breaks the :cir-

cuitiof the.- -ringin relay- .47;- at the springs 11D andwfprins :a oeking circuit-'afor itself through its QWIl.=SPrl;HgS"1'2l,-;S6 that! it will not denergizeF :and pause the ringingrelay towagainiopc'mtc whendhencalledlsubseriber Y hangsup 'hisTreoei-ven v A win the abovedescription was; assumed line "and :howthe csvllihgiisubscribcr and the Whenever a line isbusv, either on account of havlng made a call org on account of hav- 233 is so affected as to cause the ,v of the I'Ltl't ing been called, its connector privatelmnk co'ntacts corresponding to the contact 105 are groululed. 'lhcret'ore, when the wiper 35 is rotated onto the contact 105 of a busy line, a connection is ('(Illll.)lt!tt5tl from ground through said contact and wiper, side switch wiper 10 (in second position), springs 122 and 123 and the relay 51 to the spring 1255 oil" the relay 100. T herefore, when this relay deiinergizes after the last impulse for the last digit is delivered, the circuit for the private magnet -l--l is not broken, but is shifted 'fron'i ground (l to the ground at the guarded private bank contact of the busy line through the relay 5 t. The private magnet ll there'lore remains energized and prevents the side switch from passing to third position to complete the talking circuit, and at the san'ietilne' the relay 5t becomes eiiergized. The relay 5-1, upon energizing, opens the circuit of the rotary magnet at the springs lllhrlisconnects itself from the private wiper and establishes a holding circuit to ground (1 through thesprings 123 and .121- and 50. Upon the closure of the springs 126 and. 127 by the energization of the-relay 51,11 connection iscompleted from the busy signaling machine through the calling line, which connection extends from the secondary wn'iding I of the induction coil through the springs 127 and 121', contact 12%), side switch wiper 41, condenser 130, thence over the heavy v I ajpath tor the voice currents.

conductors through [the selectors I and E and the cord (.l to the calling substation and back over theotlna' side of the line to and through the upper winding of the connector line relay 15 to the battery lead 75, thence back to the secoi'idary winding of the induction coil 51 of the busy signaling machine U. The current which is supplied over this circuit by the busy signaling machine, is before stated; is an intermittent alter nating current of comparatively high frequency, but of rather low volume. Some of this current flows to ground through the alternating relay coils 302 and 20;; of the trunk I (Fig. 2), causing said rel crate to interrupt the circuit of therelay 233. It willbe understood that as alongas the busy current passing through the relay 202, the energizing circuit of the relay armature I 2;},3 wan back. This a rn'iaturc therefore reflla ins back as long as the busy current passes through'tl'ie coil 202. Furthermore, 1' be understood that the busy. tone pro cing apparatus is so arranged as to ac nue to send a busy tone for a suffieientlengthof time betweencach interruption a yelav 234 to fall Mack. 23% will fall back once *l t v lse, if it so be designateill "The relay 233, upon 11 energizing, interrupts the circuit of the -manu.cr heretofore ci 'plained to o p i relay 23 1, which i n tux n, upon dei nergizing, short-circuits the high ['L Jtanee relay 72, thereby decreasing the reslstamze 1n the c1rcuit of the cord relay L 1 si'dliciently to cause will thus be seen that at the smile time the calling subscriber receives an audible busy buzzin his receiver, tlie A-operator rt a visual indication of the busy cmnlitionof the called line, so that it the calling sub Stil'llJt-l' does not underetaz'ld the significance ofthe busy signal, or not prompt .to hang up his receiver, the operattamay inform him 'erbally that the line called isbusy and release the 'wnnection. The relay 231 in the trunk l pretera )ly hg tly slow acting, so that it will nct be caused to short: circuit the relay T2 b any single n'ujnnentary separation of the springs 21.2 and 215 of the alteri'iating cm. rent relay, so as not to give a false operation of the lamp 13 in 'eives else the alternating cmfrent relay shouldat any time receive a single impulse, such, for instance, as it might ieceive when thevkey K is restored from its (merated to its normalposition. When. the called subscriber answers, the alternating current relay is dis ci'inniiictcd from the line, so asnot to form This disconnection aceoinplishezl by the deel'iergization of the rel: '3', the i:.:ircuit olt' ivl'iiel'r is broken at the springs 232 when the current in the relay l6 s reversed upon the response of the radial subscriber, in the After the couvcrsatimi has been con'mleted, the operator is given one disconnect signal by the called subscriber hanging up -his receiver. This action breaks tlu circuit of the backbridge relay 4J3 attht springs 300. Upon the relay 4.6 d'eiinergizing, the dirtaztion of the How of te'urrent tl'rough the relay 16 is again revel sedand is now of the proper direction to cause the springs 77 and 1 to be closed. The closing of the springs 77 lights the lamp 15. :11 d the Vt sing of the springs 212 closes the circuit of the relay 233, which energizes t) close the circuit of the slow acting relay 'EEIfi-t. Upon the relay 2254 becoming energized, the shunt is re- IIIOYBtlflOlT] the high re stance relay 72, which, when. placed in the circuit of the relay 11, reduces the current through the latter sufl iciently to (ause its cleenergization, allowing its arm: ture to drop back to remove the shunt from the lamp 13 and causing it to light. gizes when the calling subscriber hangs up his receiver and lights the lamp 12. i The operator thereupon removes the pl ugs of the (he relay 10 d nercord C from the jacks. By the removal of the plug '1 from the jack J, the circuit of the relay 158 is broken, which relay, upon denel'gizing, destroys the holding circuit of the relay 6?) The relay 65, upon denergizing, destroys the bridge across the trunk conductors 67 and 68 through the relay 16, allowing said relay tofdenergize to extinguish the lamp 15 and at the same time the relay 45 of the connector H denergizes and breaks the circuit of the relay 92, which, upon deenergizing, closes the circuit of the release magnet 48, said circuit being traced from ground Gr through the springs 97- and 98, springs 99' and3143, contact of the "normal spring 49 and through said magnet 29 of the selectors F and E are destroyed.

The relay 29, u on deenergizing, closes the circuit of the re ease magnet 32, which. magnet, upon denergizing, restores the shaft to normal position and its circuit is broken by the shaft reaching its lowest po ion, as'in the case of the connector switc H. The selector F releases in the same manner as the selector E.

The B-operator is provided with a. push button 145, by means of which she may open the bridge across the trunk and release the automatic switches in case an error is made in the operation of the calling device.

It will thusbe seen that I have devised a very eflicient system in which the operator is advised .of the fact that the called line-is busy.' F rthermore, it will be seen that it is not nece. ary to provide any special arrangem'ent in connection with the connector, but that the ordinary form of connector and busy signaling machine can be employed. The only change necessary resides -in the equipment in the trunk line at the B-operators board. 1

While I'have illustrated anddescribed one particular embodiment of my invention, it is to be understood that I do not wish to be limited totheexact construction and arrangement of apparatus and circuits shown and described, but that various modifications can be made without departing from the What I claim as my invention is 1. In a telephone system, subscribers lines, means including an operators cord circuit and an automatic switch for establishing a connection between two of said lines, a vis-. ual signal in said operators cord, means for transmitting a busy tone current to the calling line when the called line is busy, and

rent to the calling line when the called line is busy, and means including two tuned vi-; brating members operated by said busy cur-v rent for intermittently operating said signal;

3. In a telephone system, subscribers lines, means including an operators'cord circuit and an automatic switch for establishing a connection between two of said lines, a supervisory signal associated with said ,cord, means for operating said signal to indicate when a called subscriber answers'and when disconnection is desired, a busy signaling machine associated with said switch for transmitting alternating current to the calling line when an attempt is made to connect with a busy line, and -means including two when a called subscriber answers and when a trunk circuit adapted to beconnected thereto and an automatic switch adapted to be connected to said trunk circuit, a signal in said cord, a bus signaling machine, means controlled there y for transmitting a busy tone current to the callin line when the called line is busy, a relay bridged across said trunk circuit responsive to said busy tuned vibrating members controlled b said signaling current, and means controlled by said relay for operating said signal. I

6. In a telephone system, a plurality ,of subscribers lines, means for establishinga connection between two of said lines, said means includingan operators cord circuit, a' trunk circuit adapted to be connected thereto and an automatic switch adapted to be connected to said trunk circuit, a signal in said cord, a busy signaling. machine,

means controlledthereby for intermittentl transmitting 2% busy tone current to the cal ing line when the" called line is busy, a relay bridged across said trunk circuit responsiveto said busy signaling current, and

means controlled by said relay for intermit tently operating said signal.

7. In a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit, a trunk circuit adapted to be connected there to and an automatic switch adapted to be connected to said trunk circuit, a supervisory signal in said cord, means for operat ng said signal for indicating the response of the called subscriber and for indicating that a disconnection is desired, a busy signaling machine, means controlled thereby for trans mitting a busy tone current to the calling line when the called line is busy, a relay bridged across said trunk circuit responsive tbsaid busy signaling current, and means controlled by said relay for operating said signal. I

8. In a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit, a trunk circuit adaptedto be connected thereto and. an automatic switch adapted to be connected to said trunk circuit, a superyi'sory signal in said cord, means for operatsaid signal for indicating the response of the called subscriber and for indicating that aldisconnection is desired, a busy signaling machine, means controlled thereby for intermittentlytransmitt'ing a busy tone current to thecalling line when the called linens busy, a relay bridged across said trunk circuit responsive to said busy slgnalmg currbnt, and means controlled by said relay for intermittently operating said signal.

9. Ina telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit,

a trunk circuit adapted to be connected 10. In a telephone system, a. plurality of thereto and an automatic switch adapted to be connected to said trunk circuit, a signal in said cord, a pair of condensers in said trunk, a bridge across said trunk on the calling side of said condensers, a second bridge across said trunk on the called side of said condensers, a busy signaling machine associated with said automatic switch for transsaid first-mentioned bridge, and means c on-.

trolled by said changc of resistance for operating said signal.

subscribers lines, means for establishing a connection. between two of said lines, said means including in operators cord circuit, a trunk circuit adapted to be connected thereto and an automatic switch adapted to be connected to said trunk circuit, a si nal in said cord, a pair of condensers in sai trunk, a bridge across said trunk on the calling side of said condensers, said bridge including a pair of relays, a third relay" bridged across said trunk: 0n the called side of said condensers, a busy signaling machine asso ciated with said switch for transmitting an intermittent tone busy current to the calling line when the called line is busy, means controlled by said current for operating said third relay, means controlled by said relay for short-circuiting one of the rela s of said calling bridge to thereby reduce t e resistance of said b ridge, and means controlled by said reduced resistance for operating said signal.

11. In a telephone system, a plurality of subscribers lines, means for establishing .a connection between two of said lines, said means including an operator's cord circuit, a trunk circuit and. an automatic switch, a signal in said ccrd, a relay bridged across said trunk, a second relayin a local circuit having normally closed contacts controlled by said first-mentioned relay, means for" transmitting a busy signaling current to thecalling line when the called line is busy,

means whereby slid signaling current operates sald first-mentioned relay to break said normally closed contacts to tl'iereby'deem;

ergize said second relay, and means controlledby the dei nergization of said second relay for operating said slgnal.

12. In a teleplione system, a plurality of,

subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit, a trunk circuit and an automatic switch, a signal in said co rd, a pair of condensers in said trunk circuit, a bridge including a resistance across said trunk on the calling side of said condensers, a relay bridged across said trunk on the called side of said condensers, a second relay ina localcircuit having a normally closed contact controlled a busy signaling current to the calling line when the called line is busy, means con-- trolled by said current for operating said first relay for breaking said normally closed contact, whereby said second'relay is deencrgizcd, means controlled by the de'einer ization of said second relay for cbangingt e resistance in said calling bridge, and means controlled by said. change in resistance for operating said si anal.

13. In a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, said conncjctiongbetw'een atrunk circuitadapte means including a cord circuit, a trunk line and an automatic switch, a signal in sand 'cord, a pair of condensers in said trunk, a

pair of relays in abridge across said trunk on the callm side of said condensers, a third n'luy br ged across said trunk on the called side of said coruleiisers, a. fourth relay in a local circuit having noru'ullly closed contacts controlled by said third relay, means for transmitting busy signaling current to the calling line when the called line isbusy, means controlled by said busy signaling current for operating said third rclay to open said normally close-til contacts to thereby deiinergize said fourth relay, :1 shortcircuit around one of the'relays in said cal.l ing bridge, means for closing said short-circuit upon the deiinergization of suidfourth' relay to thereby reduce the resistance in said callingbridge, and means controlled by said reduced resistance for operating said signal.

14. In a telephone system, a plurality of subscribers lines, means for establishinga. connection between two of said line said means including an operators cord circuit, a trunk circuit adapted to be connected thereto and an automatic switch adapted to be con nected to said trunk circuit, a signal in said cord, :1 pair of condensers in said trunk, a bridge across said trunk on the calling side of said condensersfasecond bridge across said trunk on the-called side of s l conden sers, means for changing the r said first-mentioned bridge when .,he subscriber answers, means controlled b change of resistance for operating said ma l, a busy signaling machine associated with an intermittent tone busy current to the calling line when the called line is busy, a relay in said second bridge responsive to said busy current, and means controlled. by said relay for changing the resistance of said first-mentioned bridge to thereby operate said signal to inform the operator that the called line is busy.

15.--I n atelephone system, a plurality of subscribers lines-"means for establishing a means incl'iidingfan' o ators' coi d circuit,

theretoand m: autpmhtic;

el connbte d tQ Sald I! It densers n of-relays, mean f control ed by e' called subscriber for decrease the resistance of said bridge, means controlled by said-decrease of resistance for operati'ri-gsaid signabej third relay bridged across said trunk on .thecalled sideof said be col'mected to said said automatic switch for transmitting lrcuit, a. signal rela bridged across said of said relays to therebyintermittent tone busy current to the calling line when the called line is busy, means con trolled by said current for operating said third relay, and means controlled by said relay for sl'iort-eireuiting one of the relays of said calling bridge to thereby reduce the resistance of said bridgc'to thereby operate said signal to inform the operator that the called line is busy.

16. In a telephone systcn'i, a plurality of subscribers lines, means for establishing a connection between two of said lines, said means including an operatofis cord circuit, :1 trunk circuit adapted to be connected thereto and an uutoiuatic switch adapted to be connected with said trunk circuit, a sig nal in said cord, a busy signaling machine, means controlled thereby for transmitting a busy tone current to the calling line when the called line is busy, a. relay bridged across said trunk circuit, sa d relay having a tuned armature responsive to said busy sigualint current, and means cmitrollcd by said relay for operating said signal.

ii". in a telephone system, a plurality of subscribers lines, means for establishing n connection between two of said lines, said means including an opcrutofis cord circuit, a trnnk circuit adapted to be. connected thereto and an automatic switch adapted to trunk. circuit, a signal in said cord, a busy s; gnaling' machine, means controlled th reby for ii'derznitt-ently transmitting: a bus .one current to the Eng line when-ti. busy, a relay across said trunk uit, said relay lllH-lltfi a tuned a-irineturc. responsive to said busy signaling current, and means con-- trolled by said relziy .t'or intermittently operating; said signal.

18. in a, tel- )lione system, a plurality of subscribers lines, means for establishiru! a, connection between two of said lines, said. means including an operators ord circuit, a trunk circuit adapted to be conmjected thereto and an automatic sn itch adapted to be connected to said trunk circuit, a super 'visory signal in said cord, means foroperating said signal for indicating the of the called subscriber and for indicating tha tga disconnection i s,desired,, abusy signetg machine, 4 means controlled thereby a mlttl11-g -a-busy tone cl'n'rent-to the ,ca lin in efl'rlie'n their-tilled line is'busy,"a.

trunk circuit, said relay h-a-vinga tuned armature responsive. to said busy sigmalingtcurrent, and means con trolled by said relay for operating said sig nal. 19. In a telephone system, a plurality of subscribers' lines, means for establishing a connection bet-ween-two'of said lines, said Inca-I18 including an opemtors cord circuit,- a, trunk circuit adapted to be connected thereto and an automatic switch adapted to response ating sai be connected to saidtrunk circuit, a supervisory signal in said cord, means for opersignal for indicating the response of the called subscriber and for indicating that a, disconnection is desired, a busy signalin-g machine, means centrolled thereby for-intermitlflntly transmitting av busy tone current ito the' calling line when the called line is busy a relay bridged across said trunk circuit, said relay having a tuned armature responsive to said busy signaling current, and mearis controlled by said relay for intermittently operating said signal.

20. In a telepl one system, a trunk line, a

relay bridged across said trunk, said relay com risin a ermancnt Ina et a air of magnetizing coils and a tuned harmonic armature, a circuit conirolled by said armature, a relay in said circuit, a signal controlled by said relay, and a tuned member operating in conjunction withsaid armature.

Signed by me at Chicago, Cook county,

Illinois, this 10th day of April, 1913.

CHARLES J. ERIGKSON. Witnesses:

ALBERT ANDEBS EN,

ARTHUR J. RA! 

